Cable testing equipment



Patented Nov. 8, I932 ssetsz $3,, HUBBARD, GE :errrsrmn, MASSACEUSEWTS, ESSIGNQE Elm G GQMPMTSZ} A @QEEQBATIOH (ill NEW EUR-3i? cunts rnsrrnu neummur Application tiled March 52 i 1 832.

My invention relates to cable testing equip ment and more particularly to such equip ment including electric valves for supplying high voltage unidirectional current writable i for high voltage cable a ln test ng of high voltage cable it is desirable to have an apparatus which will supply a sufficiently high voltage to piclr out spot hi the insulation or create a fault therein; ([23) carbonize a path through the fault reduce its resistance to a relatively low value, and (3) send out an inter. pted direct current through the fault so thatits ocation may l e determined by any suitable fault detection apparatus, for example, an exploring coil and associated phones or indi cating instruments.

l-leretofore there have been devised certain arrangements including electric valves, suit able for supplying extremely high voltage unidirectional currentfor testing high volt age cable equipment. The arrangements of the prior have generally utilized two electrode high vacuum pure electron discharge valves heceuse of their suitability for operation at extremely high voltages Such arrangements are particularly suitable for producing a fault at a weak spot in the insulation of a cable under test. An example of such equipment is described and claimed in my Patent l lo. l,867,4(l7 July i2, 193%, and assigned to the same assignee as the present application After the production of a fault, as described above, it is desirable to increase the current through the fault sufiiciently to car bonize the fault, that is, to decrease its resistance, and thereafter to supply intermittent unidirectional current through the fault which may be detected by any suitable fault detecting means, such for example, as an exploring coil together with car phones or instruments etc. While apparatus embodying my invention and having the latter characteristics is most useful as a complement to testtil ' ing equipment of the type disclosed in the aforementioned application, in certain instances it may be capable also of initially producing a fault in the cable, that is, completely testing the cable.

It is an object of my invention therefore to Serial No. 600 9118.

provide an improved cable testing equipment which will supply sujficient high voltage unidirectional current to carhonize a fault in a cable and which will thereafter supply intermittent unidirmtional current to provide for on the detection of the fault.

it is another object of my invention to proan improved cable testing equipment which initially supply to the cable suficient current to carbonize a fault in the cable so will thereafter supply intermittent unidirectional current impulses and which in cludes means for deener ing the testing euuipment in response to a normal fault curllwlliis accordance my invention a cable to he is connected to be energized from an alternating curent circuit through rectify ing means including a vapor electric discharge valve, preferabiyprovided with acout-rcl grid for regulating the amount of current transmitted therethrough. The grid of the electric valve is connected to be energized from the alternating current circuit through a motor driven reversing switch, the eifect of which is to render the valve conductive when the grid potential is of the same polarity as the anode potential, and to render the valve non-conductive when these two potentials are of opposite polarit There is also provided disconnecting means for the rectifier which operates in response to abnormal fault current to momentarily .deenergize the rectifying means.

For a better understanding of my invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. The single figure of the accompanyin drawing illustrates an arangement embo ying my invention for supplying high voltage unidirectional testing current to a cable from a source of alternating current.

Referring now to the drawing, there is illustrated an arrangement for supplying high voltage unidirectional current to a cable 10 from a source of alternating current 11 The cable 10 is illustrated as comprising a aeeaeea mittent unidirectional impulses to if'ie cable 2. In an equipment for testing a cable comprising a piurality cf insulated cenductive elements, the combi-i tion a? a source oi alternating current, a high voltage transformer, a pair of grid controlled vapor electrio valves comprisingwi said transformer a controlled rectifier, etions from the direct current circuit of said rectifier for em citing the conductive elements of said cable, a circuit for connecting the grids of said valves to said alternating current circuit, and means for periodically reversing the connections of said grid circuit for supplying intermittent unidirectional impulses to said cable.

3. In an equipment for testing a cable comprising a plurality of insulated conductive elements, the combination of a source of alternating current, rectifying means for interconnecting said source and the conductive elements of said cable including a vapor electric valve provided with a control grid, means for energizing said grid from said source, means for periodically reversing the polarity of the grid potential for supplying intermittent unidirectional impulses to said cable, and means responsive to abnormal fault current for'momentarily deenergizing said rectifying means.

In witness whereof, I have hereunto set my hand.

HORACE S HUBBARD.

H. c. HUEGLIN 1,886,683

VBNTILATING MEANS Original Filed June 30,. 1928 as x 17 18 7 11 it/6n? 

